The present invention relates to an apparatus for producing an ion beam of high current density and more specifically to an end-Hall ion source.
Ion beams are useful for a wide variety of applications. Surface treatment of materials by ion beam include ion implantation or coating. Processes can produce improvements in surface hardness, friction properties, wear resistance, fatigue life and oxidation resistance, among other benefits. Ion bombardment can improve adhesion in a vapor deposition process or can be used to roughen or chemically alter a surface to improve bonding of adhesive connections. Surface treatments using ion beam technologies have been applied to a wide range of materials including metals, polymers, ceramics and glasses. Many of the same results that are conventionally produced by chemical vapor deposition, ultraviolet radiation treatments or other processes may be achieved by ion beam processing of materials.
Moreover, ion beams are of considerable use in manufacture and processing of semiconductors, both for etching and for deposition. Unfortunately, conventional ion beam sources tend to produce high energy beams which can cause damage to surfaces rather than treating them. Many lower energy ion beam sources have very low current densities resulting in overly long processing times. Hall-effect ion sources have been pursued as a possible solution to these problems. For example, an end-Hall ion source such as disclosed in Kaufman et al. (U.S. Pat. No. 4,862,032) has been proposed for providing ions for processing applications. The Kaufman device, however, suffers from both of the above mentioned problems, producing an ion current of only about 1-4 mA/cm2 containing ions that are accelerated to a few hundred volts, an energy level that is too high for some applications.
To overcome the drawbacks of conventional end-Hall ion sources the present invention provides a high current density ion source which is capable of delivering ions at a low voltage including: an end-Hall effect ion source having a vacuum chamber, for producing an ion beam; and a plasma generator, arranged to produce a plasma in the vacuum chamber to supply ions to the ion source.
Another aspect of the present invention provides a high current density ion source, including a vacuum chamber, a gas injector, constructed and arranged to inject a gas which is ionizable to produce a plasma into the vacuum chamber and a target, disposed at one end of the vacuum chamber. A radio frequency electromagnetic field source is disposed outside of the vacuum chamber and constructed and arranged to provide a radio frequency electromagnetic field in a plasma generating region within the vacuum chamber, the electromagnetic field ionizing the gas to produce a plasma. A magnetic field source is disposed outside of the vacuum chamber and constructed and arranged to produce a magnetic field for guiding the plasma and a cathode is disposed within the vacuum chamber, between the plasma generating region and the target and having an opening therethrough, such that ions traveling from the plasma generating region to the target pass through the opening in the cathode.
Yet another aspect of the present invention provides a method of processing a substrate with ions which includes providing a vacuum chamber, a substrate located at an end of the vacuum chamber in a target area, a gas in the vacuum chamber which is ionizable to form a plasma, and an electromagnetic field in a plasma generating region within the vacuum chamber, thereby ionizing the gas to produce a plasma. Further, a magnetic field for guiding the plasma is provided along with a cathode within the vacuum chamber. The cathode has an opening therethrough, such that ions traveling from the plasma generating region to the target area pass through the opening in the cathode.